Piston



PISTON 3 Sheets-Sheet 1 IAHHQVTCHL FLOYD FI KISHLJNE BYg l' HIS ATTORNEY Sept. 21, 1948.

Filed June 19, 1942 4 9 9 M 0 2 L 6 I w m .M I o u 9 6i 0 M RMB m 82 m M M98 1 I m r- 0 H P 1943- F. F. KISHLINE 2,449,657

rxs'rou Filed June 19, 1942 3 Sheets-Sheet 2 Til/ 700 III/IIII/l/ Ill/[1111101111 INVENTOR. FLOYD F. msnum;

HIS ATTORNE Sept. 21, 1948. F. F. KlsHLiNE 2,449,657

PISTON Filed Jun 19, 1942 I y a Sheets-Sheet 3 INVENTOR. FLOYD F. KISHLINE" m ATTORNEY Patented Sept. 21, 1948 Floyd r. Kishline, Kenosha, Wia, alsignor to Nalh-Kelvlnator Corporation, Kenosha, Wia, a

. corporation of Maryland Application June 19, 1942 Serial No. 447,836

This invention relates to a piston and is more particularly directed to a piston for usein internal combustion engines.

It is quite common in the art to manufacture pistons of iron or steel castings ior' internalcombustion engines although such pistons have undesirable qualities in so far as the transmission of the heat of combustion away from the combustion chamber is concerned. Such pistons must be provided, as a general rule, with a relatively thick head wall in order towithstand the heat of combustion developing within the combustion chamber without producing hot spots, burn outs and the like. Too thin a "wall in the head region will result in hot spots appearing which will eventually lead to burn outs. By increasing the wall thickness at .this region, the danger of burn outs is prevented but the heat transmittin qualities of the head are reduced.

Pistons have also been manufactured or aluminum castings. which material is a much better conductor of heat than cast steel or cast iron.

Aluminum. however, has a much higher coeffi- .cient oi.,expansion than cast iron, of which the ton has warmed up to proper operating tempora ture. Additionally, aluminum is considerably more expensive than is cast iron or steel.

The steel or cast iron pistons, however. have approximately the same rate of expansion as the cylinder wall with which they are used and can be fitted rather closely at relatively low temperatures with the assurance that these fits will be maintained at operating temperature. The principal difliculty with cast iron or steel is that, due to the previously mentioned head thickness, the heat-is not conducted away from the combustion chamber as rapidly as is the case with aluminum and it is therefore not possible, as a general rule, to employ compression ratios in connection with cast iron or steel as high as those employed with aluminum; consequently, knocking or detonation caused by self-ignition of the 'combustibles in the combustion chamber is much more prevalent in connection with iron or cast steel-than is the case with aluminum.

The piston of the present invention has been 19 Claiml- (Cl. 30914) 2 designed with a view to taking advantage or the similarity oi coemcients or expansion oi the cylinder wall and a steel piston and yet to make provision forrapid conduction oi. heat away from the head of the piston by providing means for cooling the piston head, which, in this instance, is a an extremely thin walled structure reinforced with a box-like section for the purpose of increasing its strength.

It is an object of this invention to provide an extremely thin walled piston made up of steel stampings and properly reinforced at its loadbearing points by further light stampings in such a way as to increasethe strength without impairing the desirable qualities flowing from thin walled sections.

It is a further object of this invention to provide'means in a piston whereby a cooling fluid may be circulated over the highly heated portions of the piston so as to extract heat therefrom rapidly and emciently.

It is a further object of this invention to permit an increase oi. the compression ratios heretofore permissible with steel pistons by using a means for eiiiciently cooling the pistons.

Other objects and advantages inherent in the he 5 line 2-'2 and looking in the direction of the'arrovvs;

Figure 3 is a vertical. longitudinal; sectional view of the piston taken upon a plane as indicated by the line 3-3 of Figure 2;

Figure 4 is a detailed sectionalview through a portion of the piston head and illustrating a step in the method of assembly of the same;

Figure 5 is a vertical, longitudinal, sectional view ofv a modifledform of the piston constituting the present invention;

Figure 6 is a horizontal sectional view through the piston shown in Figure 5 taken upon a plane as indicated by the line 6-6 of Figure 5 and looking in the direction of the arrows;

Figure 7 is a vertical sectional view similar to Figure 8 showing a still further modification of the invention;

Figure 8 is a horizontal sectional view-oiv the piston taken upon a plane as indicated by the line 8-8. of Figure 7 and looking in the direction of the arrows; 1

Figure- 9 is a vertical, longitudinal. sectional view through a piston representing a still further modification of the invention; E

Figure 10 is a horizontal sectional view taken upon a plane as indicated by the line l8-l8 of Figure 9 and looking in the direction of the arrows;

Figure 11 is a plan view of a still further modifled form of the piston;

Figure 12 is an elevational view of the piston shown in Figure 11;

Figure 13 is a horizontal sectional view through a piston taken upon a plane as indicated by the line i8l8 of Figure 12;

Figure 14 is a vertical, longitudinal, sectional view taken upon a plane as indicated by the line IL-Il 01' Figure 12;

Figure 15 is 'a sectional view taken upon a plane as indicated by the line i8--l'8 of Figure 11; and Figure 18 is a plan view of the inner shell shown in Figures 1a, 14 and 15.

' Referring in more detail to the drawing in which similar reference characters are employed throughout to designate similar parts, the invention will be recognized as residing in a piston 28 which is connected through a piston pin 22 to a connecting rod 28 which is supported upon a crank pin 28 from a crankshaft 28 of an internal combustion engine. Crankshaft 28 is supported in bearings (not shown) which may be supplied in the usual manner with lubricating oil from a pressure lubricating system. The crankshaft is drilled throughout its length as at 88 to receive pin 28 with the oil outlet 88. The hearing insert 38 may be maintained against rotation within the Q crank pin end of the connecting rod by any suitable means and is aligned in its thus fixed position with two apertures constituting entrances to oil passageways l4 and 88. The oil passageway 88 terminates upon the upper side of the crank pin end of the connecting rod in a metered nozzle 88 which is adapted once during each rotation of' the crank pin to emit a stream of .oil therefrom. This stream of oil will be emitted as the piston approaches its top dead center position to cause a deposit of lubricating oil upon the walls of the I cylinder indicated at 88. The oilpassageway 88' extends upwardly centrally of the connecting rod 28 for the purpose of supplying oil within the wrist pin eye 82 of the connecting rod 28.

The wrist pin eye 82 is hushed. as at 88 and such bushing is provided with a groove 88 exthereto. The upper or head end of the outer.

shell 88 having an upper. reduced cylindrical portion 82 of smaller diameter than the skirt portion 88 and concentrically arranged with respect stamping is provided with an integral wall 88 forming a closure for. the upper end of the piston. such wall being rovided with a downwardly drawn centering depression 88 for the purpose of receiving a tool, as will be shortly explained. The lower end of the skirt 88 of the outer shell is provided with an inwardly and upwardly'fianged portion which may be conically shaped upon its inside for receiving a centering 8001.

The portions 88 and 88 are provided for the purpose of permitting the reception of the piston, after it has been completed, within a grinding machine. the piston being centered upon the tending completely therearound. The upper .end

of the connecting rod terminates in a'drillednozzle 88 which is adapted to emit a'stream of oil against the underside of the head of the piston 28 once during each revolution of the crankshaft.

surfaces 88 and 88. It will be understood, of course, that these are not employed until the entire piston has been assembled and welded to its final shape.

Nested within the outer shell 88 is an inner reinforcing member 18. Inner sheli'lil may take the form of a shallow cylinder having oppositely disposed ribs 12 upon its front and rear surfaces and extending vertically with respect to the piston. Depending from the underside of the shallow cylinder forming the principal part of the inner shell 18 are ears It which may be located at the front and rear of the piston and form, in a sense. extensions of the ribs l2,

Returning for the moment to the outer shell 88 and referring specifically to Figure 3, it will be noted that the outer shell is provided with depressions 18 at opposite sides thereof and located wardly flanged portions 18 of the outer shell.

The wrist pin bushing spans both cylindrical flanged elements I8 and 88 on one side of the piston, two such bushings being employed, and serves rigidly to connect the inner and outer shell adjacent the sides of the piston. The piston pin 22 is located lengthwise within the bushings 88 by means of snap rings 28. d

The upper end of the inner shell is closed by an end wall 88, such end wall being provided with .an elliptical opening 88 surrounded by an up .wardly extending fiange 88. The opening 88 is I arranged with its longaxis extending transverse- 1y of the piston or in the same plane as the plane of rotation of the crank pin 28 so as to permit a relatively long sweep of the oil nozzle 58 during respect to the piston head the ,oil received through the opening 88. The end closure 88 of the inner shell is spaced from the end closure 88 of the outer shell by -The piston shown in' Figure 1 is made up of means of a sinuously corrugated steel ribbon 82. This ribbon is relatively thin with respect to its,

width and corrugations are employed for the purpose of stabilizing it so that it may be stood on its edge as shown in Figures lthrough 4. The corrugated ribbon82 is fashioned into a rosette form as shown in Figure 2. Ribbon 82 may be provided along its lower edge with a series of notches 84 which extend through only about a quarter of the width of the ribbon. Notches 84 permit oil which is trapped within the rosette to flow to the outside of the rosette in order that the oil may act as a cooling fluid both on theinside and outside of the corrugationsformed by the ribbon and against the underside of the entire surface of the piston head 84.

Oil which has been sprayed from the nozzle 88.

has struck the downward projection formed by the depression 88 and been deflected over the top edge of the flange 88 of aperture 88 will rest upon A portion of the oil so circulated will be re- 8 turned along the inner wall or the outer shell by means of the grooves 88 formed by the ribs I2. Oil flowing through the grooves and down the inside of the outer shell 88 will be trapped at the lower edge of the piston by the upwardly flanged portion 88 and will be returned 'to the reservoir through apertures I88 arranged at thebottom oi the trough I82 formed by the flange 88. Apertures I88 will direct the oil accumulated in the trough I82 against the cylinder wall 88 and will serve as means for lubricating the cylinder wall 88 in addition to nozzle 48. 3

Attention is directed to Figure 4 which shows the method of assembly of the outer shell 88, inner shell I8 and'the rosette formed by the ribbon 82.

The parts are shown in Figure 4 as loosely assembled just prior to the operation in which they are pressed intocontact with one another. It will be understood that the outer surface of the cylindrical portion 18 of the inner shell has a pressed fit with the inner surface of the reduced cylindrical portion 82 of the outer shell as shown in Figure 4. The outer shell 88 is inverted. the

rosette dropped in place upon the inside surface of the head closure 84 with-the notches 82 upwardly disposed in this position and then the inner shell 18 is placed within the reduced cylindrical portion 82 of the outer shell and forced down into position. It will be noted that the head or end wall 84 of the outer shell 88 is shown slight- 1y dished in Figure 4 while the end closure 88 of 5' through the rosette and to closure and the dishing which is apparent in Figure 4 in the head 84 will be flattened out so that each of these parts is returned to a single plane and each part is seated throughout its extent upon adjacent portions of the rosette. This seriatim seating of the rosette edge portions upon both the inner and outer headforming elements insures solid contact throughout the entire extent of the edge portions of the rosette with both of these elements and makes it possible later to perform a hydrogen welding operation upon the entire piston. Solid-contact of the rosette with both parts and the subsequent hydrogen welding provide for efficient heat transfer from head 84 88. The reduced cylindrical portion 82 of the outer shell 88 is provided for the purpose of forming 'a seat for a plurality of flanged rings I88.

Flanged rings I88 are pressed downwardly over the outside of the reduced cylindrical portion 82 into abutting relationship with one another and with their flanges outwardly extending and spaced.

from one another. It will be noted that the rings 7 I88 do not extend completely to the top surface v 84 of the outer shell and the gap left between the topmost ring I88 and the head of the outer shell "84 is filled by means of a U-shaped ring I I8 which may he made up of two parts of similar section which are reversed and secured to one another as by resistance welding, The inner edge I I2 of the U-shaped ring H8 may be secured as by tack welding at II4 to head 84 to hold the rings I88 in place 'I'he grooves which are formed between the flanges of the rings I88 are adapted to receive piston rings II8 such as are usually provided upon the pistons of internal combustion engines.

However, before the piston rings I I8 are assembled upon the piston. it is necessary to secure all 'of the other elements. making up the piston to one another in a permanent fashion and this is accomplished by so-called hydrogen welding. which comprises heating the piston in the presence of a copper brazing material and in a hydrogen atmosphere. This operation causes the flow of the copper brazing material to all of the joints and results in a uniting of the parts through these joints by means of the copper. After the brazing bly has been made the subject matter of a oothe inner shell is shown as being slightly .de-

formed upwardly. The rosette formed by the ribbon 92 is. however, of uniform vertical extent throughout and consequently that portion of the rosette toward the center of the piston will be the first to seat upon both the under surface of the head 84 and upon the upper surface of the closure 88 as the inner shell I8 is pressed upwardly into place.

Attention is directed to the clearance I84 existclearance I88 which exists between the bottom surface of the rosette and theuppper surface of the inner shell head closure 88. As the assembly operation continues. the upwardly deformed pending application of Floyd F. Kishline for. Method of assembling a piston, Serial No. 551,357. filed August. 28, 1944. now Patent No. 2,437,824.

After final grinding, the lowermost ring I88 may be drilled at spaced intervals as shown at II8, the aperture extending through the upper reduced cylindrical portion 82 of the outer shell so as to provide means for returning tothe reservoir oil scraped from the cylinder wall by the lowermost or oil piston ring.

Referring to the modification shown in. Figures 5 and 6, the same type of outer shell 88 is employed having a reducedcylindrical upper portion 82 and using a rosette made up of corrugated ribbon 82, the'prlncipal difference between the piston shown in Figures 1 to 4 and the piston in Figures 5 and 6 residing in the inner shell.

In this instance the inner shell "8 is flat'ted of! adjacent the conical depressions I8 and extruded flanges I8 of the outer shell 88 to form end closure 88 will be returned to a single plane a flat wall III which extends downwardly ad- 7 v iacent each side of the inner shell I16 and transversely of the piston and is provided with a pierced and extruded portion to form flanges I64 for receiving the piston pin bushing I60. oil which is received through the flanged aperture I66 and distributed laterally by means of the oil to the oil reservoir. Radially extending ribs I13 may be provided in the head I66 of the inner shell to reinforce the same.

The inner shell I also differs from the inner shell of the first modification in that the flanged aperture I66 is circular in outline although still centrally placed in the closure I66 of the innershell.

Instead of employing a plurality of flanges t form piston ring grooves, this piston utilizes a sleeve, 200 of cast iron in which the piston ring grooves 202 may be cut as by turning. The sleeve 200 is held in place against the shoulder of the outer shell by means of a stamped ring 203 which may be secured as by tack welding 204 to the head portion of the outer shell. The space 205 within the ring 203 is vented by means of apertures 206 to the interior of the piston. These apertures 206 function to prevent overheating of the space within the ring 206 such as might be likely to cause the ring to buckle and distort. Oil return apertures 2! may be drilled through the reduced diameter 62 of the outer shell and the sleeve 200 in order to provide an outlet return to the reservoir for oil which is scraped from the piston walls by the action of the oil ring, which constitutes the lowermost of the piston rings.

Referring to Figures 7 and 8, which constitute a further modification, it will be noted that in this instance the outer shell 260 is formed along lines generally similar to the outer shell 60 of Figures 1 and 6 but the shell is not provided with an integral head closure; instead the upper edge of the reduced portion 262 terminates in a flange 263 providing an upwardly presented flat surface, the inturned edge of the flange being serrated as at 266 to provide seats for locating and aligning the bights forming the periphery of the rosette. After the ring sleeve 202 is placed -in position, an end closure 264 is fitted to the ring sleeve 202' and is pressed downwardly apertures 206 are again provided for the P611 of relieving the pressures that may build up due to the heat within the'space 206 at the upper periphery of the piston.

Referring to Figures 9 and 10, it will be noted that in this modified form of the piston the outer shell 666 has a reduced cylindrical portion 662. The upper. extremity of the .outer shell terminates in an inwardly flanged rin 666. Ring 6661s made up of a series of radially has a downwardly extending annular flange 664 is adapted to be secured as by hydrogen welding to the surfaces of the lands 661 and 666.

It will be noted that the underside of the flange 666 slopes downwardly and outwardly for the purpose of more efficiently conducting cooling oil therealong in contact with the under surface of the head closure 664. It will also be understood that the underside of the downwardly extending depression 666 acts to distribute oil laterally into the channels formed by the. lands 361 and 666. Oii thus directed will flow radially outwardly into the space 606 formed by the downwardly extending flange 666 of the head closure 664 and will be returned to the oil reservoir'through the apertures 606 in the upper portion of the reduced cylindrical upper part 6620f the outer shell 660. Oil may be returned to the reservoir as it is scraped off the cylinder wall by theoil ring by means of the apertures 3I8 extending through the cylindrical portion 662 and the piston ring sleeve 662.

Against the underside of the flanged portion 666, there is secured as by welding an inner shell 610 formed to flt within the reduced cylindrical portion 662 but also provided with flat transversely extending side wall portions '6". Side wall portions 611 may be grooved as at 616 for strengthening purposes. The upper edges of the flat wall portions 61I of the inner shellj616 are against the upwardly presented surface of the annular flange 266. The flanged edge 265 of the end closure 264 terminates upon'the ring sleeve at the level of the upper edge of the upper piston ring groove and has a pressed fit with the ring sleeve 202. The inner shell 210 is again provided with flattened portions 21I extending transversely to the axis of the piston pin and these flattened portions are provided intermediate their extremities with astrengthening rib 216, strengthening ribs 212 being provided adjacent the sides of the piston in the inner shell and extending from top to bottom thereof for the purpose of conducting oil therethrough. The corrugated ribbon 92 is again employed for the purpose of spacing the inner shell from the head closure 264 and is received within serra-.

tions 256 as previously explained. Venting flanged as at 616 for attachment to the underside.

of the inner shell flanged portion666. It will be noted that the flanges 616 terminate adiacent the sides of the piston and that the inner shell is cut away as at 66L It will also be noted to the walls "I but instead are bent to align with the under surface of the flanged portion 666 which is arranged to drain oil radially outwardly of the piston. 7

Referring to Figures 11 to 16, a still further modification of the invention appears. In this instance the outer shell 460 is formed as a unitary stamping complete with the upper reduced portion 462 and a head closure 464. An inner shell 410 is provided which has a cylindrical portion 412 arranged to have a pressed flt with the inner cylindrical surface of the reduced cylindrical portion 462 of the outer shell. The upper surface of the inner shell 416 comprises a generaliy'flat under surface "I in which there are the lands 416 form channels for the-purpose of conducting cooling oil radially outwardly in con- :tact with the head closure 484 and into an an- ,[nular space 411 formed by the conical upper side walls 419 of the inner shell 410. Oil within the cylindrical portion 462 by a pair of flanged rings 4I0 secured as at 2 to the outer end closure 464. Provision for venting the volume within the rings 4ill may take the form of apertures 2 extending through the wall 482.

It will be understood that in all of the modifications described, the component parts of the .piston are similarly secured to one another by a hydrogen brazing process. It has been found that this process functions excellently to preserve the parts in their original relationship under all conditions of heat encountered within the cylinder; This end result is believed to be due, to a large extent, to the use of the cooling oil which is sprayed against the underside of the head and distributed by the channel forming means once during each revolution of the crankshaft. It has been found that in spite of the high temperatures encountered upon the piston head, there is no visible carbonization of the oil and that no varnishing effect of the oil is apparent after many hours of testing under very severe conditions. This is believed to be due to the fact that fresh quantities of cool lubricant are constantly being ejected against the piston head and are removing the heat at its point of application rather than requiring the heat to flow downwardly along the piston wall and be transferred across the juncture of the piston and cylinder wall and into the cooling water in' the jacket Bl (see Figure 1). This removal of the heat before it is required to travel any appreciable distance improves the wear of both the piston and-thev cylinder wall as the lubrication conditions of the cylinder wall are considerably improved due to its operation at a much lower temperature'than previously.

While the invention has been described in considerable detail, the foregoing description is not to be taken as limiting but simply as illustrating the invention. All equivalents falling within the scope of the appended claims are hereby expressly reserved. a

I claim: 1 g 1. A piston comprising an outer cylindrical stamping, the side walls of said stamping being extruded inwardly of said stamping to form aligned apertures along a diameter of the piston, an inner stamping nested within said outer stamping and secured to said outer stamping, de-

pending portions on said inner stamping spaced inwardly from said outer stamping and apertured and flanged in alignment with the extruded and flanged portions of' said outer stamping, and bearing sleeves positioned in said aligned apertures at each end of said diameter.

2 A piston comprising an outer cylindrical stamping having side walls extruded inwardly of said stamping to provide cyiindrically flanged aligned apertures along a diameter of said stamping, an inner stamping nested within said outer stamping and having depending portions spaced I 10 laterallyfmm the side ing and pierced and extruded along said diameter to provide cylindrically flanged apertures aligned with the flanged apertures in said outer stamping, and a bearing sleeve secured within said aligned apertures and spanning the space therebetween at each end of said diameter.

3. A piston having an-euter stamped shell, asmaller inner stamped shell within .said' outer shell, and means securing said outer and inner shells together comprising means closing the head of-said outer shell, means forming an end wall of said inner shell. means spacing said head closing means and said end wall from one another and securing them in spaced relation to form a strengthening element, and means adjacent the end of said'inner shell opposite said end wall securing said inner and outer shells in spaced relationship.

4. An internal combustion engine havin an oil distributing system, a crankshaft,.a connecting rod carried by said crankshaft, and a piston having a head and carried by said connecting rod, means for supplying oil from said system to the underside of said piston head and retaining it in contact therewith comprising, an oil nozzle in said connecting rod adjacent the underside .of

ranged aperture, and peripherally arranged apertures located adjacent the periphery of said baille.

6. A piston comprising an outer shell. a head closing the end of said outer shell, a baffle arranged within and spanning said Outer shell, means spacing said baiile below said head, said baille providing a centrally arranged aperture, flanges projecting upwardly around the periphery of said aperture. and other apertures located adjacent the periphery of said baille.

'7. 'A piston for an internal combustion engine comprising an outer cylindrical shell, means forming a closure for one end ofv said shell, an inner shell nested within said outer shell and having an inner end wall spaced from said closure means, means connecting said closure means and end wall in spaced relation with respect to one another, and means upon a diameter of said outer shell spacing said inner-shell therefrom,

8. A piston for an internal combustion engine comprisingan outer shell having an end closure, an inner shell nested within said outer shell and having an end wall, a spacer member located between said closure and wall and in contact therewith at spaced points, and means securing said spacer member to said outer and inner shells to hold said wall and closure so spaced.

9. In combination with an internal combustion engine having a pressurelubricating system, a piston comprising a shell having a skirt and a head, a baille located within said shell and spanning the interior thereof below said head, means spacing said bame from said head over a portion.

only of said head to provide channels extending radially of said head, an inlet formed in the cenwalls of said outer stamp-' nels, and means for delivering lubricant from said pressure systemto said bame inlet.

10. A piston having an outer shell, a smaller inner shell within said outer shell. and means se-' curing said outer and inner shells together comprising means closing the head said outer shell, means forming an end wall of said inner shell.

and a rosettedribbon-arranged between and spacing said head closing means and. said end wall from one another and secured thereto to form a structural head strengthening element.

11. A piston having an outer shell, a smaller inner shell within said outer shell, and means securing said outer and inner shells together comprisingmeans closing the head or said outershell,

means forming an end wall of said inner shell, and

means adjacent the end of said inner shell 0W0- site said end wall securing said inner'and outer shells in spaced relationship. a

12. A piston having an outer shell, a smaller inner shell within said outer shell, and means securing said inner and outer; shells together comprising means closing the head of said outer. shell, means forming an end wall of said inner shell,

' and a thin metallic ribbon arranged with its width vertically disposed and having one of its edge portions united with said head closing means and the other or its edge portions united with said end wall to term a structural head strengthening element.

13. A piston having an outer shell, 9. head for said outer shell, an inner shell nested within said outer shell and having an end wall located adiacent to but slightly spaced from said head, a corrugated metallic ribbon arranged in the space .between said end wall and head, and means securing said ribbon to said end wall and head respectively.

- 12 inwardly irom said outer stamping and apertured and iianged in alignment with the extruded and flanged portions or said outer stamping, and hearing sleeves positioned in said aligned apertures.

at each end oi said diameter and secured therein as by brazing. said piston being relieved oi'ali tinitial stresses as a result'oi said brazing opera- 17. A piston having an outer stamped shell.

a smaller inner stamped shell within said outer shell. and means securing said outer and inner shells together comprising means closing the head "comprising an outer stamped shell, an inner stamped shell press-fitted within said outer shell, a head on said outer shell, an end wall on said inner shell, means spacing said head and end 14. A piston having an outer shell, a head for said outer shell, an inner shell nested within said outer shell and having an end wall located ad- Jacent to.,said head, corrugations in said end wall forming radially extending channels below said head. and means securing said end wall and head together.

15. A piston comprising an outer shell. a head for said outer shell, a central downwardly extending projection upon said head, an inner shell nested within said outer shell, an end wall for said inner shell having a central aperture aligned with said projection, means spacing said end wall irom said (head to provide channels therebetween. and

means securing said parts together. 16. A piston comprising an outer cylindric stamping. the side walls oi. said stamping being extruded inwardly oi the stamping to form aligned apertures along adiameter or the piston. an inner stamping nested within said outer stamping and secured to said outer stamplns y brazing. depending portions on said inner stamping spaced wall from one another to torm coolant channels therebetween, an inlet to said channels at the center or said end wall? and outlets from said channels ,around the periphery oi the piston, said parts being secured together in final position as by brazing, the piston being substantially free of initial stresses as a result 0! brazing.

'19. A piston for an internal combustion engine comprising an outer cylindrical stamping having a lowerportion or large diameter and an upper portion or relatively reduced diameter with a top wall extending across the end thereof, an inner stamping nested within said outer cylindrical stamping and having an end wall. a spacer member located between said top and end walls and in contact therewith at spaced points, and means securing said spacer member to said outer and inner stampings to hold said walls so spaced.

FLOYD F. KISHLINE.

I nnrnanivcns crrnn The following references are of record in the ills of this patent:

'Uurrnn s'rs'ras rams Number ,Name Date 1,073,197 Westinghouse Sept. 16, 1913 1,468,670 Taylor septrs, 1923 1,513,718 Soulis 4.----- Oct. 21,1924 1,838,852 Carlson May 17, 1927 2,142,175 Buttner .Jan. 3, 1939" 2,174,644 Welthei'head et al. Oct. 3.1939 2,841,836 Wood Feb. 15, 1944 

